Low pressure exhauster system



y 1964 A. Y. DODGE 3,134,239

LOW PRESSURE EXHAUSTER SYSTEM Filed Nov. 19, 1962 INVENTOR. Aou= Y. DODGE United States Patent C) ice Filed Nov. 19, 1962, Ser. No. 233,455

'- 8 Claims. (Cl. 62-170) This invention relates to a low pressure exhauster system and more particularly to an apparatus for pumping large volumes of vapor or the like at low absolute pressures and is a further improvementon the low pressure exhauster shown and illustrated in my Patent 3,007,322. In handling vapors and the like at low absolute pressures for evaporating a liquid from a container or containers, or similar closed space or spaces, it becomes necessary to pump extremely large volumes of very low density fluid. Piston pumps and rotary vane pumps become too large to be practical for this purpose and centrifugal pumps are extremely inefficient due to the low density of the fluid. I

It is therefore one of the objects of the present invention to provide a low pressure exhauster which functions with a high degree of efficiency to pump large volumes of vapor and the like at an extremely low absolute pressure.

Another object is to provide a low-pressure exhauster in which a portion of the vapor to be pumped is withdrawn from a container by a mechanical pump and is compressed thereby, the compressed vapor being supplied to a jet ejector connected to an adjacent container to withdraw an additional and larger volume of vapor therefrom.

According to a further feature of the invention, the principles thereof may be incorporated in a closed cooling system using water or similar liquid as a cooling medium by evacuating vapor from a container under low pressure, condensing the vapor and returning the condensate to the original container. In such a system an auxiliary vacuum pump is preferably provided and is automatically controlled to maintain a predetermined degree of subatmospheric pressure in the system.

The invention is also applicable in evaporating systems either for dehydration or distillation by supplying a liquid to be evaporated to a container and collecting the condensate in a third container from which it may be removed by a pump.

The improvement comprising this invention lies in part by the introduction of a separate but adjacent container in which different degrees of low pressure are maintained for evaporating purposes. The mechanical pump evacuating one chamber maintained at a higher pressure than the second chamber which is evacuated by jet exhauster type vacuum pump. The two chambers are connected to pass fluid from the higher pressure chamber to the lower pressure chamber; automatic control means are provided to control the fluid level and pressure diflerential between the two chambers.

Various other applications of the invention as wellas other objects and advantages thereof will be more readily apparent from the following descriptionwhen read in connection with the accompanying drawing which shows a diagram of an elevation with parts in section of a low pressure exhauster system employing the invention.

As shown in the figure, which shows the complete system, partly in cross-section, a liquid or similar material to be subjected to low pressure is enclosed in two conp.s.i.a.

3,134,239 Patented May 26, 1964 tainers 9 and It The upper part of container 9 above the normal level of liquid therein is connected to the inlet of mechanical pump 11 which is driven by a motor 12. The upper part of container 16 is connected through a conduit 13 to a jet ejector, indicated generally at 14, as shown in my co-pending application Serial Number 129,689. The jet ejector comprises an outer tubular casing 15 defining an outer passage communicating with the conduit 13 and a central nozzle 16 connected through a conduit 17 to the discharge opening of the pump 11. A reduced throat 13 is providedbeyond the discharge nozzle 16 and communicates with a vortex chamber 19. Vapor is passed through a condenser 21 for cooling purposes. A cooling medium, such as air, may be circulated by a fan 23. Cooling of the vapor condenser 21 will condense vapor entering the condenser chamber and the condensate will drain from the bottom of the condenser chamber through a conduit 24 passing a check valve 25 into a separate container 26. A vacuum pump 27 is connected to the upper part of the third container 26 and is driven by a motor 28 controlled by a swtich 29 re- A sponsive to the pressure inthe container 26 to maintain a constant static pressure therein. Condensate collecting in the container 26 may be withdrawn therefrom by a liquid pump 3%. w

The containers 9 and it) may be supplied with liquid to be evaporated through an inlet connection 31 controlled by a valve 32 and communicating with any desired source of liquid. A pump 3'23 may be connected to the lower part of the containerrlil to remove liquid therefrom when desired.

For various uses of-the exhauster, the containers 9 and Ill may form a part of heat exchangers which are completed by a coil 34 in the container 10 and having external connections 35 and a similar coil 34' in container 9. A second fluid may be circulated through the coils 34 and 34' in heat exchanging relation with the material 7 in the containers 9 and it? for various processes employing the exhauster.

Condenser 22 is optional equipment, may be used to extract heat from the compressed vapor leaving pump 11, if desired. It may be a fluid to fluid condenser. Its cooling medium may be circulated through coil 34 when desired, as indicated by connection 35'.

Vapor passing from container 9 may be bubbled up through fluid in container 19, thus making use of a portion of the differential pressure to be maintained between containers 9 and 10.

One useful purpose of the exhauster is to provide a secondary cooling system for use in cooling apparatus, as more particularly disclosed and claimed in my copending application Serial Number 43,460. For this purpose, water can be used as the cooling medium. The

containers 9 and M will be filled with water to a level below the connection to the pump 11. In this case, the outlet port of the pump 39 will be connected through the valve 32 to the supply port 31 of the container 1th to recirculate the condensate in a .closed cooling cycle.

Preferably for cooling, the static pressure in the system is reduced by the vacuum pump 27 to approximately 2.5 When the pump 11 is operating, it will reduce the pressure in the upper part of the container 10 to about .5 p.s.i.a. and will compress the vapor so Withdrawn to about 10 p.s.i.a. The compressed vapor discharge through the nozzle 16 will induce flow of a substantially larger a volume of vapor from the upper part of the container at about .5 p.s.i.a. and the mixture of vapors will discharge into the vortex chamber 19 at about 2.5 p.s.i.a. As the vapors are condensed, they will flow by gravity into container 26 and can be returned by the pump 30 to the container 10 in a closed cycle. The pressure and temperature in the first container may be indicated by a suitable gauge 36 and thermometer 37.

For this use of the exhauster, the coil 34 may serve as a condenser for a primary refrigerant which is circulated therethrough in a closed refrigerating cycle. The water in the container 9 or 10, or both, will be maintained at a relatively low temperature by evaporation with the heat ultimately being dissipated to the air from the condenser 21.

In one example of this use, let it be assumed that it is desired to exhaust 120 cubic feet per minute of water vapor from the containers 9 and 10 at a pressure of .5 p.s.i.a. at 80 F. Water vapor at the .5 p.s.i.a. and 80 F. weighs pound per cubic foot and is at very low density. The pump 11 will pump about 30 cubic feet per minute of water vapor from the container 9 and will discharge compressed vapor at 10 p.s.i.a. and about 220 F. This hot vapor is mixed with two to three volumes of cool vapor in the ejector and due to this mixing and to the subsequent reconversion of flow to pressure, the vapor will discharge into the condenser 21 at about 130 F. The hot vapor will be cooled by the condenser to approximately atmospheric temperature and the condensate will be collected in the container 26 and returned to the first container 9 at a temperature some 10 above ambient temperature. Therefore, with the present apparatus a pump having a capacity of about one-fourth of the total volume of vapor to be pumped can be employed so that the apparatus does not become excessive in size and can function with a high degree of efficiency.

In using the invention for evaporating as, for example, in a distilling operation, the liquid to be distilled is supplied to the container 9 through the valve 32 and inlet port 31 and is evaporated under the same conditions as described above in connection with cooling. In this operation, heat may be supplied to the coil 34 as, for example, by circulating hot water or steam therethrough to increase the rate of evaporation. The condensate collected in the container 26 may be withdrawn therefrom by the pump 30 and taken to the inlet 31 or to another desired point of use. The enriched liquid remaining in the containers 9 and 10 may be withdrawn therefrom by the pump 33 either periodically or continuously, depending upon the material being evaporated.

The apparatus may also be used for dehydrating or concentrating operations by placing the liquid to be dehydrated or concentrated in the container 16 and proceeding in the same manner as in an evaporating operation. When the material has reached the desired degree of dehydration or concentration, it may be withdrawn from the container 10 by the pump 33. Alternatively, Where the material is dehydrated to complete dryness, the container 10 could be opened and the dried material removed therefrom in a batch process.

It will be apparent that in addition to the operations specifically described, the invention could be employed in any process wherein it is desirable to pump large volumes of vapors or similar fluids at low pressure and the specific uses enumerated above are intended only to be examples of those to which the invention may be applied.

The above temperatures and pressures are given merely as an illustration. Other pressures, temperatures, and volumes, may be used.

It should be understood that suitable valve and pressure means and level control means are employed to maintain a low pressure in container 10 and a somewhat higher low pressure in container 9 in the order of 4 p.s.i.a. in container 9 and 1 p.s.i.a. in container 10. For

this purpose, I have illustrated a pressure control valve 50 operated by an accordion bellows 51 to maintain a lower pressure in container 10 and a float valve 32 operated by a float 52 to maintain a fluid level in container 9. Other suitable means may be employed to control level and pressure in these two containers.

What is claimed is:

1. A low pressure exhauster comprising a pair of containers defining spaces to be exhausted, a pump having an inlet and an outlet, a first conduit connecting the upper part of the first space to the pump inlet whereby the pump will withdraw vapor therefrom and increase the pressure on the vapor, a jet ejector including two passages, a second conduit connecting one of the passages to the pump outlet to receive vapor under increased pressure therefrom, and a third conduit separate from the first conduit connecting the other of said passages directly to the second space, discharge of the vapor under increased pressure through said one of the passages inducing flow of a larger volume of vapor from the second space through the third conduit and the other of the passages, and means to connect the first container with the second container to pass fluid from the first container to the second container, and control means to regulate the pressure existent in the two containers.

2. In a cooling system, first and second containers adapted to contain a liquid to be cooled, a pump having its inlet connected to the upper part of the first container to withdraw vapor therefrom and to compress the vapor, a jet ejector including two passages, a connection from one of said passages to the upper part of the second container to receive vapor therefrom, a connection from the outlet of the pump to the other of said passages, a condenser receiving vapor discharged from the jet ejector and condensing it, a third container receiving condensate from the condenser, a connection from the third container to the first container to return condensate to the first container, the containers and connections forming a closed system, and a vacuum pump connected to said system to maintain a predetermined static pressure therein.

3. The system of claim 2 including means in the first containers to circulate a fluid therethrough separate from but in heat exchanging relationship with the liquid in the first containers.

4. In an evaporator system, a plurality of containers, a first container adapted to contain a liquid to be evaporated, a pump having its inlet connected to the upper part of the first container to withdraw vapor therefrom and to compress the vapor, a jet ejector including two passages, a connection from the upper part of the second container to one of said passages for flow of vapor therethrough, a connection from the outlet of the pump to the other of said passages to supply compressed vapor thereto, a condenser receiving vapor discharged from the jet ejector and condensing it, means to supply liquid to be vaporized to the first container, a third container receiving condensate from the condenser, a vacuum pump connected to the upper part of the third container to maintain a subatmospheric pressure therein, a liquid pump connected to the lower part of the third container to withdraw condensate therefrom, and means connecting the first container with the second container to pass fluid from the first container to the second container, and control means to regulate pressure existent in the two containers.

5. The evaporating system of claim 4 including means in the container to circulate a fluid therethrough separate from but in heat exchanging relationship with the liquid in the container.

6. The evaporating system of claim 4 including a control for the vacuum pump responsive to the pressure in the third container.

7. In an exhauster system, a plurality of chambers to be exhausted, mechanical exhauster pump to exhaust one chamber to a mediumly low absolute pressure, a jet type exhauster pump to exhaust the second of said chambers to an absolute pressure below that of the first chamber, said ejector pump motivated by the discharge pressure from said mechanical pump, means connecting the first chamber with the second chamber to pass fluid from the first chamber to the second chamber, and control means to regulate the pressure maintained during operation in the two chambers.

8. A low presure exhauster system comprising two spaces connected in series to be exhausted by a mechanical pump and a jet pump connected in parallel, said mechanical pump exhausting vapor from the first space, delivering it to the nozzle of the ejector pump, the ejector pump exhausting vapor from the second space, and means to connect the first space to the second space comprising automatic controls to maintain lower pressures in the second space than in the first space.

References Cited in the file of this patent UNITED STATES PATENTS 3,007,322 Dodge Nov. 7, 1961 

8. A LOW PRESSURE EXHAUSTER SYSTEM COMPRISING TWO SPACES CONNECTED IN SERIES TO BE EXHAUSTED BY A MECHANICAL PUMP AND A JET PUMP CONNECTED IN PARALLEL, SAID MECHANICAL PUMP EXHAUSTING VAPOR FROM THE FIRST SPACE, DELIVERING IT TO THE NOZZLE OF THE EJECTOR PUMP, THE EJECTOR PUMP EXHAUSTING VAPOR FROM THE SECOND SPACE, AND MEANS TO CONNECT THE FIRST SPACE TO THE SECOND SPACE COMPRISING AUTOMATIC CONTROLS TO MAINTAIN LOWER PRESSURES IN THE SECOND SPACE THAN IN THE FIRST SPACE. 